1. Field of the Invention
This invention relates to plasticized metal neutralized sulfonated EPDM terpolymers having at least 65 wt. % of ethylene in the backbone of the EPDM terpolymer and extended compositions of these metal neutralized sulfonated EPDM terpolymers having 100 parts of a neutralized sulfonated EPDM terpolymer; less than about 100 parts per hundred of a non-polar process oil; less than about 300 parts per hundred of a filler; and a preferential plasticizer at about less than 60 parts per hundred based on 100 parts of the sulfonated elastomeric polymer. These compositions can be readily processed due to their superior rheological properties on conventional plastic fabrication equipment, especially on low pressure injection molding and extrusion equipment into elastomeric articles having improved physical properties.
2. Description of the Prior Art
Recently, a new class of thermoelastic sulfonated polymers has been described in a number of U.S. Patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as Butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer having substantially improved physical properties over an unsulfonated elastomer at room temperature. However, these ionically cross-linked elastomers may be processed like a conventional thermoplastic at elevated temperatures under a shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at the elevated temperatures thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or basic materials selected from Groups I, II, III, IV, V, VIB, VIIB and VIII and mixtures thereof of the Periodic Table of Elements. Although these sulfonated elastomeric polymers prepared by the process of this patent are readily useable in a certain number of limited applications, they are not as readily adaptable for the manufacture of an injection moldable elastomeric article such as footwear as are the improved compositions of the present invention, wherein both improved physical and rheological properties are realized. U.S. Pat. No. 3,642,728 fails to teach, imply or infer the criticality of selection of the basic EPDM to be sulfonated, wherein the EPDM terpolymer must have an ethylene content of at least 65 wt. percent in order to obtain improved physical properties.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines. The resultant ionically cross-linked sulfonated elastomers prepared by this process do not exhibit both the improved physical and rheological properties of the compositions of the present invention, since U.S. Pat. No. 3,836,511 fails to realize the criticality of selection of an EPDM with a high ethylene content.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. C. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic acid ester. Additionally a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonate groups at a temperature of forming. The compositions formed by this process are not as suitable for the manufacture of high performance elastomeric articles such as footwear formed by an injection molding process as are the compositions of the present invention, since U.S. Pat. No. 3,870,841 fails to realize the criticality of using an EPDM terpolymer with at least 65 wt. percent ethylene in order to obtain systems having improved physical properties.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer. This patent again fails to teach the criticality of selection of the EPDM terpolymer in order to obtain maximum physical properties.
U.S. Pat. No. 3,887,530, herein incorporated by reference, demonstrates that partly crystalline EPDM's can be sulfonated and neutralized to produce materials which are superior in physical properties to those obtained from amorphous EPDM systems. These materials of themselves are not desirable because they are very difficult to process and mix. This patent does not teach, imply or infer how these improved products can be processed in conventional extrusion and injection molding operations. This patent further fails to teach the differences in melt viscosities that are obtained through the use of different metal counterions in the metal sulfonate group and that the zinc counterion is outstanding in this regard from all the rest. This patent fails to teach that metal sulfonate high ethylene content EPDM's can be transformed into processable thermoplastic elastomers through the use of the appropriate cations and the appropriate ionic domain plasticizer.
Products resulting from the aforementioned methods for obtaining neutralized sulfonated elastomeric compositions, do not possess the improved balance of rheological and physical properties for the applications envisioned in the present invention.
For example, the physical properties of these resultant patents are unsuitable for a major application of an injection molding process, namely the manufacture of a ski boot. The materials of the aforementioned patents which are generally processable by only compression molding have unsuitable physical properties for this major application of ski boots. Additionally, the metal neutralized sulfonated EPDM terpolymers of the instant application can be used in the manufacture of medical tubing by an extrusion process, wherein excellent strength and increased flexibility are desired properties which was previously unattainable by employing the compositions of the aforementioned patents.
Increasing the ethylene content in the backbone of the EPDM improves the physical properties substantially over lower ethylene content products. The unplasticized gums, however, possess high melt viscosities and of themselves cannot be processed and are difficult to mix. Quite unexpectedly the use of select ionic domain plasticizers, notably zinc stearate, not only substantially improves melt flow so that the plasticized gums are processable and mixable but also maintains and even improves the physical properties of the base system. The improvements in physical properties and in melt flow through the use of high ethylene content EPDM's and zinc stearate plasticizer are also present in the extended compositions containing fillers and oils.
The unique and novel improved metal neutralized sulfonated EPDM terpolymers and their extended compositions of the present invention overcome the deficiencies of the aforementioned U.S. Patents by providing an improved balance of rheological and physical properties. The blend compositions of the present invention solve the problem of having a material which has both desirable rheological and physical properties for the manufacture of an elastomeric article such as a ski boot, automotive parts such as facia, bumper guards and the like.